Defaults: Manage Default Argument Values for quantmod Functions

Description

Use globally specified defaults, if set, in place of formally specified default argument values. Allows user to specify function defaults different than formally supplied values, e.g. to change poorly performing defaults, or satisfy a different preference.

Usage

setDefaults(name, ...)
unsetDefaults(name, confirm = TRUE)
getDefaults(name = NULL, arg = NULL)
importDefaults(calling.fun)

Arguments

name

name of function, quoted or unquoted

...

name=value default pairs

confirm

prompt before unsetting defaults

arg

values to retrieve

calling.fun

name of function to act upon

Value

setDefaults: None. Used for it's side effect of setting a list of default arguments by function.
unsetDefaults: None. Used for it's side effect of unsetting default arguments by function.
getDefaults: A named list of defaults and associated values, similar to formals, but only returning values set by setDefaults for the name function. Calling getDefaults() (without arguments) returns in a character vector of all functions currently having defaults set (by setDefaults).This does not imply that the returned function names are able to accept defaults (via importDefaults), rather that they have been set to store user defaults. All values can also be viewed with a call to getOption(name_of_function.Default).
importDefaults: None. Used for its side-effect of loading all non-NULL user- specified default values into the current function's environment, effectively changing the default values passed in the parent function call. Like formally defined defaults in the function definition, default values set by importDefaults take lower precedence than arguments specified by the user in the function call.

Details

setDefaults

Provides a wrapper to R options that allows the user to specify any name=value pair for a function's formal arguments. Only formal name=value pairs specified will be updated.

Values do not have to be respecified in subsequent calls to setDefaults, so it is possible to add new defaults for each function one at a time, without having to retype all previous values. Assigning NULL to any argument will remove the argument from the defaults list.

unsetDefaults

Removes name=value pairs from the defaults list.

getDefaults

Provides access to the stored user defaults. Single arguments need not be quoted, multiple arguments must be in a character vector.

importDefaults

A call to importDefaults should be placed on the first line in the body of the function. It checks the user's environment for globally specified default values for the called function. These defaults can be specified by the user with a call to setDefaults, and will override any default formal parameters, in effect replacing the original defaults with user supplied values instead. Any user-specified values in the parent function (that is, the function containing importDefaults) will override the values set in the global default environment.

Examples

Run this code

my.fun <- function(x=3)
{
  importDefaults('my.fun')
  x^2
}

my.fun()        # returns 9

setDefaults(my.fun, x=10)
my.fun()        # returns 100
my.fun(x=4)     # returns 16

getDefaults(my.fun)
formals(my.fun)
unsetDefaults(my.fun, confirm=FALSE)
getDefaults(my.fun)

my.fun()        # returns 9